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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Regression of 3.13.1 with iterator creation being duplicated","articleBody":"# Bug report\n\n### Bug description:\n\nFor my Python compiler Nuitka, I use CPython as the oracle of what  the correct behaviour is. I am running some tests that I used to clarify the behavior from decades ago, in this case I wanted to know when exactly the iterator creation is used. I striped this test a bunch, so the regression is still visible. I first noticed the issue on GitHub Actions, where 3.13.0 got replaced with 3.13.1 for Windows and Linux, but it applies to all OSes. See below for a diff, that the same iterator is created multiple times.\n\n```python\n\"\"\" Generator expression tests\n\n\"\"\"\n\nfrom __future__ import print_function\n\nimport inspect\n\nprint(\"Generator expression that demonstrates the timing:\")\n\n\ndef iteratorCreationTiming():\n    def getIterable(x):\n        print(\"Getting iterable\", x)\n        return Iterable(x)\n\n    class Iterable:\n        def __init__(self, x):\n            self.x = x  # pylint: disable=invalid-name\n            self.values = list(range(x))\n            self.count = 0\n\n        def __iter__(self):\n            print(\"Giving iterator now\", self.x)\n\n            return self\n\n        def __next__(self):\n            print(\"Next of\", self.x, \"is\", self.count)\n\n            if len(self.values) \u003e self.count:\n                self.count += 1\n\n                return self.values[self.count - 1]\n            else:\n                print(\"Raising StopIteration for\", self.x)\n\n                raise StopIteration\n\n        # Python2/3 compatibility.\n        next = __next__\n\n        def __del__(self):\n            print(\"Deleting\", self.x)\n\n    gen = ((y, z) for y in getIterable(3) for z in getIterable(2))\n\n    print(\"next value is\", next(gen))\n    res = tuple(gen)\n    print(\"remaining generator is\", res)\n\n    try:\n        next(gen)\n    except StopIteration:\n        print(\"Usage past end gave StopIteration exception as expected.\")\n\n        try:\n            print(\"Generator state then is\", inspect.getgeneratorstate(gen))\n        except AttributeError:\n            pass\n\n        print(\"Its frame is now\", gen.gi_frame)\n\n    print(\"Early aborting generator:\")\n\n    gen2 = ((y, z) for y in getIterable(3) for z in getIterable(2))\n    del gen2\n\niteratorCreationTiming()\n\n```\n\nThe unified diff between 3.13.0 output (and basically all Python versions before) and 3.13.1 output.\n\n```\n\n--- out-3.13.0.txt      2024-12-06 12:37:19.447115100 +0100\n+++ out-3.13.1.txt      2024-12-06 12:37:23.452239500 +0100\n@@ -1,9 +1,11 @@\n Generator expression that demonstrates the timing:\n Getting iterable 3\n Giving iterator now 3\n+Giving iterator now 3\n Next of 3 is 0\n Getting iterable 2\n Giving iterator now 2\n+Giving iterator now 2\n Next of 2 is 0\n next value is (0, 0)\n Next of 2 is 1\n@@ -13,6 +15,7 @@\n Next of 3 is 1\n Getting iterable 2\n Giving iterator now 2\n+Giving iterator now 2\n Next of 2 is 0\n Next of 2 is 1\n Next of 2 is 2\n@@ -21,6 +24,7 @@\n Next of 3 is 2\n Getting iterable 2\n Giving iterator now 2\n+Giving iterator now 2\n Next of 2 is 0\n```\n\nThe duplicated prints out the iterator creation are new. This is not optimal and new. I don't know if the iterator being through a slot cause cause this or what it is. I checked if `generator.c` changed but I think it didn't at all.\n\nMy self compiled Python 3.13.1 for Linux and the official Windows download agree in behaviour.\n\n### CPython versions tested on:\n\n3.13\n\n### Operating systems tested on:\n\nLinux, Windows\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-132351\n* gh-132384\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/kayhayen","@type":"Person","name":"kayhayen"},"datePublished":"2024-12-06T11:45:20.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/127682/cpython/issues/127682"}